A variety of packers are used in wellbores to isolate specific wellbore regions. A packer is delivered downhole on a tubing string and a packer sealing element is expanded against the surrounding wellbore wall to isolate a region of the wellbore. Often, two or more packers can be used to isolate several regions in a variety of well related applications, including production applications, service applications and testing applications.
In some well applications, slat packers are used to isolate specific regions of wellbores. Slat packers generally are able to support higher differential pressures and higher expansion rates because the slats act as an efficient anti-extrusion barrier for an internal bladder. Slat packers are formed with a tubular rubber bladder covered by metallic slats to support the internal pressure and the mechanical stress to which the packer is submitted. The slats are oriented longitudinally so as to have a high recovery ratio, however the recovery ratio decreases during inflation of the packer. As the packer is inflated, the slats generally slide over each other, but the packer remains totally covered by slats when fully inflated. A rubber sleeve is placed over the layer of slats along their exterior to avoid external leaks between the regions of the well isolated by the packer.
The ability to prevent extrusion of the tubular rubber bladder is important in high-temperature packers because constituents of the internal bladder lose their elastic and mechanical quality at high temperatures. With a slat packer, the internal bladder acts against the layer of slats. However, inflation and deflation of slat packers can be difficult at high hydrostatic pressure because the pressure inside the packer is not balanced with the pressure of the fluid in the well. As a result, the slats are pressed between the internal rubber bladder and the external rubber sleeve which limits the ability of the slats to slide with respect to each other. After several cycles of the packer, unwanted gaps can occur between slats and render the packer susceptible to extrusion of the tubular rubber bladder. Additionally, the rubber material of the sealing layer created by the rubber sleeve also limits the expansion of a slat packer. If the packer is substantially expanded, the rubber material can tear and create a leak. The use of more elastic materials, however, can result in loss of the elastic properties that allow the rubber material to retain its shape after expansion. As a result, the slat packer can be difficult to deflate in a satisfactory manner when such materials are utilized.